Burner assemblies for metalspraying guns



Oct. 31, 1961 v. NAVARA BURNER ASSEMBLIES FOR METAL-SPRAYING cums Filed Nov. 13, 1958 IN V EN TOR.

United States Patent 3,006,555 BURNER ASSEMBLIES FOR NIETAL- SPRAYING GUNS Vaclav Navara, Ledec upon Sazava, Czechoslovakia, as-

slgnor to Kovo-Finis, narodni podnik, Ledec upon Sazava, Czechoslovakia Filed Nov. 13, 1958, Ser. No. 773,731 4 Claims. (Cl. 239-83) This invention relates to burner assemblies for metalspraying guns of the kind in which a metal wire or a stream of metal powder carried by a jet of air is fed through a central bore in the assembly and is melted and sprayed by an annular flame through which it passes. The flame is produced by an oxygen-acetylene or other suitable gaseous fuel mixture and is surrounded by an annular jet of air which serves to cool the assembly. When metal powder is used, the air jet serves also to concentrate the stream of powder, while, when metal wire is used, the air jet serves to promote atomisation of the metal and to shield from the flame an annular shield which projects from the assembly around the base of the flame.

It is essential that there should be the least possible mixture of the annular air jet with the flame in order not to reduce the flame temperature and thus the output of the gun and also, when wire is used, to prevent the air from being heated and from cooling the shield less efliciently. Some admixture of the air jet with the flame cannot be prevented as gases flowing side-by-side will always mix, particularly if the flow is turbulent. In burner assemblies of current design the fuel mixture and the cooling air leave the assembly through concentric rings of jets and there is considerable turbulence in the gas flow down stream of the jets and considerable admixture of the cooling air with the flame.

It is an object of this invention to provide a burner assembly in which the turbulence in the flow of the cooling air is minimised so as to reduce the admixture of the cooling air with the flame.

According to the present invention a burner assembly for metal-spraying guns comprises a ring burner having a. central bore for the passage of metal to be sprayed, an annular nozzle for cooling air surrounding the burner and means providing passages leading to the intake of the annular nozzle and extending parallel to the axis of the burner.

The use of an annular nozzle reduces the turbulence in the fiow down-stream of the nozzle as compared with the flow from a ring of jets while the passages leading to the nozzle serve both to streamline the flow of air to the nozzle and thus reduce turbulence in the flow through the nozzle and to increase the area of the surface of the assembly exposed to the cooling air and thus to promote more efficient cooling.

In a preferred construction in accordance with the invention the assembly comprises a tubular burner body formed with a plurality of fuel-mixture outlets arranged in one of its ends in a ring around its bore, and with separate inlet passages for a combustible gas and for oxygen communicating with said outlets, and a housing for the burner body surrounding, the same and spaced in part therefrom to provide an annular nozzle around the aforesaid end of the burner body, one of said parts, preferably the burner body, being formed with radial slots to provide air passages leading to said nozzle.

A burner assembly for a metal-spraying gun using metal wire will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIGURE 1 is an axial section through the burner assembly on the line A-B in FIGURE 2, and

FIGURE 2 is a radial section on the line C-D in FIG- URE 1.

Patented Oct. 31, 1961 The burner assembly comprises a housing part 1 in which a burner body formed in two parts 2 and 3 is held by a screw threaded sleeve 6 screwed into the part 1 and forming part of the assembly. A shield 4 is held onto the end of the sleeve 6 by a cap nut 7 screwed onto the sleeve.

Oxygen is admitted into the assembly through a port a provided in the housing part 1, acetylene through another port b and cooling air through a third port c. The oxygen passes through an annular passage d provided in the burner body part 2 and flows therefrom through a plurality of passages e to co-axial passages of a larger diameter. The acetylene is drawn in from an annular passage g into the passages f by the oxygen current. The passages f discharge into an annular passage h, from which the oxygen-acetylene gas mixture flows into a plurality of outflow passages i in the burner part 3. The passages i open in the end face of the part 3 of the burner body to form a ring of jets. This arrangement promotes turbulent flow of the fuel mixture down-stream of these jets as is desirable in order to promote rapid combustion and a hot flame.

The fuel mixture burns at these jets and heats and melts the metal wire (not shown) inside a chamber j within the shield 4, the metal wire being fed through a bore k extending throughout the burner body. An insert 5 of fireproof material is fitted in the outlet end of the bore k.

The cooling air flows from the port 0 through the annular space 1 between the sleeve 6 and the burner body and passes through slots m milled out of the part 3 of the burner body into an annular space 11. Hence the air flows through an annular nozzle p between the part 3 and the shield 4. The air stream flows from the nozzle p along the inner wall of the shield 4-, thus enveloping the flame. Through the mouth 1' of the shield two separate gas currents pass. The outer one is an air current, the inner one is the flame coming out at a high speed from the chamber j and atomising the metal ahead of the mouth of this chamber, the metal having been heated up and partially melted inside this chamber.

Because the pressure inside this chamber j is greater than the atmospheric pressure, the burning gases would tend to escape through the clearance around the wire and the bore k into the inner space of the gun. To prevent this, a plurality of oblique passages s are provided in the part 3 through which air is admitted to the bore k from the annular space n. The air currents thus created produce in the space around the wire a dynamic overpressure preventing the return of the burning gases.

The passage of the air through the slots m and annular space p reduces its turbulence greatly as compared with the burners known hitherto. This results, on the one hand, in a more efficient cooling of the shield 4 with the same amount of air and, on the other hand, in a higher output of metal sprayed with the same amount of oxygen and acetylene, as the flame in the arrangement according to the invention can heat the metal along a longer path.

It is obvious that a similar effect can be obtained by forming slots m in the sleeve 6, but cooling is not then so eflicient. When the burner assembly is to be used with metal powder, the portion of the sleeve 4 projecting from the cap 7 is omitted so that this element is no longer a shield and only forms the outer wall of the nozzle p.

-I claim:

1. A burner assembly of a metal-spraying gun, the assembly having a front and a rear end and comprising at least a single burner member and at least a single nozzle member, the burner member having a longitudinal axis and being formed with an axial bore for the reception of the metal to be sprayed, the bore extending from the rear end to the front end, the nozzle member spaced- 1y surrounding the burner member and defining therewith passages for cooling air, said passages including grooves and an annular space, the grooves extending in a generally axial direction from points at the rear end side of the burner assembly to points at the front end side and being circumferentially spaced, the annular space being provided at the front end, the grooves discharging into the annular space.

2. In the burner assembly according to claim 1, said grooves being equidistantly provided in the burner mem- 10 2 13 3 her.

3. In the burner assembly according to claim 1, the burner member having a front face and being provided with through channels for a combustible gas mixture,

the through channels being spacedly arranged about said axis and extending in a generally axial direction to terminate in said front face.

4. In the burner assembly according to claim 1, an expansion chamber being provided between said grooves and annular space.

References Cited in the file of this patent UNITED STATES PATENTS Binder Nov. 15, 1928 2,361,420 Shepard Oct. 31, 1944 2,397,165 Shepard Mar. 26, 1946 2,551,276 McMahon May 1, 1951 2,799,487 Aghnides July 16, 1957 

